The present invention relates to a magnetoresistance effect composite head and a method of forming the same.
The magnetoresistance effect composite head comprises a magnetoresistance effect head for reproduction in combination with an inductive head for recording. As the magnetic recording medium has been scaled down and has increased in capacity, a relative speed between the readout magnetic head and the magnetic recording medium is reduced, for which reason the magnetoresistance effect head has become attractive because of independence of reproduction output from the relative speed. The magnetoresistance effect head is disclosed in IEEE Transaction on Magn. MAG7, 1970, 150 entitled "A Magnetoresistivity Readout Transducer".
The most useful magnetoresistance effect head is the magnetoresistance effect composite head which comprises a magnetoresistance effect head for reproduction in combination with an inductive head for recording. The magnetoresistance effect head comprises a magnetoresistance effect element sandwiched through magnetic isolation layers made of an insulator by a pair of first and second magnetic shielding films S1 and S2. The inductive head comprises a coil sandwiched through insulators by first and second magnetic poles P1 and P2 and a magnetic gap provided between the first and second magnetic poles P1 and P2, wherein the first magnetic pole P1 comprises the second magnetic shielding film
The magnetoresistance effect composite head has a serious problem in that a large side fringe magnetic field 13 generated when recording. The side fringe magnetic field is caused by leakage of magnetic flux due to a difference in size or width between the first and second magnetic poles P1 and P2. This side fringe magnetic field prevents minimization in width of the tracks. This means that the side fringe magnetic field limits the maximum density of the track. In order to increase the density recording, it is required to reduce the side fringe magnetic field.
The conventional inductive head to be used for recording and reproduction is so formed that, of the first and second magnetic poles, side faces defining the track width are the same on air bearing surfaces facing to the magnetic recording medium, so as to reduce the side fringe magnetic field.
By contrast, in the magnetoresistance effect composite head, the width of the second magnetic pole P2 defines the track width whilst the first magnetic pole P2 is required to be wide for shielding the magnetoresistance effect element, for which reason the first magnetic pole P1 is much wider than the second magnetic pole P2. This large difference in width of the first and second magnetic poles P1 and P2 causes the side fringe magnetic field extending in lateral direction beyond the width of the second magnetic pole P2.
In the Japanese laid-open patent publication No. 7-262519, it is disclosed to reduce the side fringe magnetic field like the conventional inductive head for recording and reproduction. FIG. 1 is a fragmentary cross sectional elevation view illustrative of an inductive head of the conventional magnetoresistance effect composite head. The inductive head of the conventional magnetoresistance effect composite head comprises first and second magnetic poles 80 and 84, a magnetic gap layer 82 on the second magnetic pole 84 and provided between the first and second magnetic poles 80 and 84, and a third magnetic pole 86 sandwiched between the magnetic gap layer 82 and the first magnetic pole 80. The magnetic field is generated between the second and third magnetic poles 84 and 86 through the magnetic gap layer 82, without any substantive leakage of the magnetic field. As a result, the side fringe magnetic field is well suppressed.
The above conventional inductive head in the magnetoresistance effect composite head is formed as follows. FIGS. 2A through 2D are fragmentary cross sectional elevation views illustrative of the conventional inductive head in the magnetoresistance effect composite head in sequential steps involved in a fabrication method.
With reference to FIG. 2A, a non-magnetic layer 82' is formed on a first magnetic layer 80' acting as a magnetic shielding layer in the magnetoresistance effect head. Frames 88a and 88b are selectively formed on the non-magnetic layer 82'. The frames 88a and 88b comprise photoresist.
With reference to FIG. 2B, a second magnetic layer 84' is selectively formed between the frames 88a and 88b by a frame plating treatment. The width of the second magnetic layer 84' is defined by a gap between the frames 88a and 88b.
With reference to FIG. 2C, the used frames 88a and 88b are removed. An ion beam milling is carried out by use of the second magnetic layer 84' as a mask to selectively etch the non-magnetic layer 82' and the first magnetic layer 80'. The first magnetic layer 80' is etched at a predetermined depth whereby the second and third magnetic poles 84 and 86 and the magnetic gap layer 82 are formed. The incident angle of the ion beam is optimally adjusted to form vertical walls of the laminated structure of the second and third magnetic poles 84 and 86 and the magnetic gap layer 82 as illustrated in FIG. 2D. The magnetic field is substantially defined between the second and third magnetic poles 84 and 86 through the magnetic gap layer. The side fringe magnetic field is well suppressed.
The ion beam milling etches not only the first magnetic layer 80' but also the second magnetic layer 84' acting as the mask. The thickness of the second magnetic layer 84' is largely reduced by the ion beam milling. The formation of the third magnetic pole 86 by the ion beam milling results in reduction in thickness of the second magnetic pole 84. For those reasons, it is required that the second magnetic layer 84' is thicker than the second magnetic pole 84 by the etching depth of the second magnetic layer 84'. This means that the frames 88a and 88b defining the second magnetic layer 84' is required to be equal to or higher than the thickness of the second magnetic layer 84'. This further means that the frames 88a and 88b comprising photoresists are required to be much higher than the thickness of the second magnetic pole 84. The increase in height of the frames 88a and 88b comprising photoresists makes it difficult to reduce the distance between the frames 88a and 88b. The minimum distance between the frames 88a and 88b is 2 micrometers. This means that the minimum width of the second and third magnetic poles 84 and 86 is 2 micrometers. The recording density is limited by the minimum width of the second and third magnetic poles 84 and 86. In order to further increase in the recording density, it is required to further reduce the minimum width of the second and third magnetic poles 84 and 96. This requirement for reduction in the minimum width of the second and third magnetic poles 84 and 96 further needs the reduction in height of the frames 88a and 88b.
In the above circumstances, it had been required to develop a novel inductive head structure in the magnetoresistance effect composite head with a further reduced track width and capable of a further increased recording density.